The present invention provides facile means for aligning web-fed media used in lenticular printing and lithographic processes. Specifically, the present invention allows for the ready transformation of traditional rolls or drums used in conventional or digital printing technologies into highly accurate guide rolls for lenticular printing. By bonding or attaching an appropriate lenticular or lenticular-like surface to one or a plurality of rollers, one may rapidly and inexpensively adapt printing presses or digital printers for high-precision lenticular printing.
Lenticular printing has been in use since the 1940's. Specifically, lenticular printing involves dividing visual images into strips, alternating the image strips and arranging the image strips under a field of lenticular lenses. Lenticular visual effects include apparent 3-dimensional depth, alternating images as a function of viewing angle (“flip”), and apparent “motion” of an object in response to viewer movement. Lenticular printing has found tremendous use in advertising and promotion. Large lenticular displays feature prominently at airports and shopping malls.
Lenticular printing relies on unique optical phenomena as perceived by a viewer. As such, lenticular printing has an extremely low tolerance level for misalignment of images relative to the lenticular lenses through which the images are seen. Lenticular printing relies on unique optical phenomena as perceived by a viewer. Each Lenticular print is usually based on a number of images, each sliced into strips, which are then interlaced with one or more other images. The lenses are lined up with each image interlace, so that light reflected off, or transmitted through, each strip is refracted in a slightly different direction, but the light from all strips of a given image are sent in the same direction. The end result is that a single eye or camera looking at the print sees a single whole image, but an eye or camera with a different angle of view will see a different image. As such, lenticular printing has an extremely low tolerance level for misalignment of image strips relative to the lenticular lenses through which the images are seen. Even small displacements or misalignment of image strips may lead change the aforementioned end result and the observer may see reflections of strips of a number of images simultaneously instead of seeing them in a consecutive manner. Lenticular printing generally works on high accuracy in the feeding and placement of lenticular printing substrate into printing machines. Small errors in printing can be costly and time-consuming. In order to produce high quality lenticular printing, the lenticular printing media and the printing apparatus should remain aligned, optionally completely, during all stages of the printing process, especially during ink transfer. A common misalignment problem involves shifting of the feed lenticular printing substrate during a printing run. Specifically, lenticular web media travel between pairs of rolls, an idler roll and an impression roll, several such pairs generally being used in series to produce complete high-quality images. Small lenticular printing substrate misalignments due to web wander or web tracking motions can cause significant reduction in quality of the highly sensitive lenticular image. Any motion or distortion of lenticular web media during printing can lead to costly and irreversible misalignment.
One method for guaranteeing alignment of lenticular web feed is described by Bravenec in U.S. Pat. No. 6,276,269. In his method, Bravenec describes a guide roll having “a band of circumferentially extending grooves formed on an outer surface of the roller.” The grooves act to align lenticular lens material that is fed into the printing machine (printing occurring on the flat side opposite the lenticular lenses).